Caitlin Todd is recruited from Secret Service to join characters Special Agent Gibbs and Anthony DiNozzo in working for NCIS. Dr. Donald "Ducky" Mallard and Abby Sciuto assist them as NCIS's medical examiner and forensics scientist, respectively. Jimmy Palmer (later replacement for Gerald Jackson, assistant to Dr. Mallard) is introduced late in the season. Ari Haswari, a terrorist enemy whose storyline would last until season three, is also introduced in this season.